1. Field of the Invention
This invention relates to a composite sheet of high strength and high softness and a method of making it. The composite sheet of this invention can also be easily made thin, light, and wear resistant and is especially suitable for artificial leather.
2. Description of the Prior Art
Conventionally, high quality artificial leather has been made by impregnating with a binder a nonwoven sheet of ultrafine fibers. However a large amount of binder spoils the softness and suppleness of the composite sheet and a small amount of binder does not bring about high strength and wear resistance to the nonwoven sheet. Therefore high softness and low elongation which is necessary for some uses did not exist together in conventional non-woven sheet.
U.S. Pat. No. 4,368,227 discloses artificial leather which comprises a woven or knitted fabric and a non-woven fabric firmly bonded to the woven or knitted fabric. However, the strength, wear resistance and the softness have their own limit, because in the known fabrics such as this, a large amount of a binder is indispensable. The reason is, in the known fabrics, very short fibers (10 mm or less) are used to ease intertwining of the short fiber by water jet with the woven or knitted fabric. The very short fibers bring about the composite sheet weakness and allow the short fibers to fall off easily. The high pressure fluid jet applied in the manufacture of these known fabrics is not suitable for intertwining short fibers of ordinary length (20 mm or more) with the woven and knitted fabric. On the other hand, needle punching which is suitable for intertwining short fibers of ordinary length has not been applicable for the same purpose because it causes breakage of the woven or knitted fabric. Further when the broken fibers are exposed on the surface of the composite sheet, the appearance is seriously damaged.